Conventionally, a printing device is known which includes a liquid supply mechanism that supplies a printing liquid such as ink or the like to a printing portion. As this kind of printing device, for example, a patent literature 1 discloses a printing device including a liquid supply mechanism that has a main tank (ink cartridge) storing ink and a sub-tank (head tank). In this liquid supply mechanism, ink in the main tank is sent by a pump to the sub-tank to be stored, and the ink stored in the sub-tank is sent to the printing portion (recording head). And, in the liquid supply mechanism, when a liquid surface of the ink in the sub-tank falls, the pump is driven to perform ink supply from the main tank to the sub-tank. And, when the liquid surface of the ink in the sub-tank rises to a predetermined positon, the pump is stopped. In this way, the liquid surface of the ink in the sub-tank is kept at a constant level and the ink supply to the printing portion is stably performed.